1. Field of the Invention
The present invention relates to plasma display panels, and in particular, to a bus electrode formed on a front substrate of a plasma display panel.
2. Discussion of the Related Art
A plasma display panel (PDP), recognized as a wide and high quality display device, expresses natural gray scales, and realizes excellent color representation, short response time, and large-scaled dimensions.
FIG. 5 is an exploded perspective view of a plasma display panel, and FIG. 6 is a plan view of an electrode structure formed at a front substrate of the plasma display panel.
The plasma display panel as shown in FIG. 5 includes two sheets of front and rear transparent glass substrates 1 and 2 facing each other, a plurality of stripe-shaped parallel transparent electrodes 3 formed on the inner surface of the front substrate, and a bus electrode 4, formed along the longitudinal side of each transparent electrode 3, with a width smaller than the transparent electrode. A transparent dielectric layer 5 covers the transparent electrodes 3 and the bus electrodes 4, and a transparent protective layer 6 is formed on the dielectric layer 5 with magnesium oxide (MgO).
Additionally, a plurality of stripe-shaped address electrodes 7, orthogonal to the transparent electrodes 3, is formed on the inner surface of the rear substrate 2. A highly reflective dielectric layer 8 covers the address electrodes 7, and a plurality of barrier ribs 9 is formed on the dielectric layer 8. The barrier ribs 9 are formed between the address electrodes 7, while proceeding parallel thereto, thereby forming groove-shaped discharge cells 10. Red, green, and blue phosphors 11 are formed in the discharge cells 10.
The PDP is assembled by facing the two glass substrates 1 and 2 towards each other, injecting a gas mixture such as Ne—Xe or He—Xe into the discharge cells 10, and sealing the peripheries of the substrates 1 and 2 with glass frit.
The transparent electrodes 3 are formed with a transparent conductive material such as indium tin oxide (ITO) or SnO2, and the bus electrodes 4 are formed with a material such as Ag or Cr—Cu—Cr, which have a sheet resistance lower than that of ITO or SnO2. As a result, the bus electrode 4 lowers the resistance of the transparent electrode 3, thereby enhancing its conductivity.
With a PDP structured as above, the transparent electrodes 3, the bus electrodes 4, and the address electrodes 7 are drawn to the outside of the substrates 1 and 2, and voltages are selectively applied to the terminals connected thereto in order to permit discharging within the relevant discharge cells 10. This discharging excites the phosphors 11 to generate visible rays, thereby displaying the desired images.
PDP quality depends upon several factors including the characteristics of brightness and contrast. Contrast is further classified as dark-room contrast and bright-room contrast. Considering that users commonly operate PDPs in a bright environment, bright-room contrast substantially affects image quality.
For this reason, much effort has been made to enhance the PDP's bright room contrast. For example, black colored bus electrodes may be formed on the transparent electrodes to try to darken the bus electrodes and improve the contrast.
However, in this case, transparent electrodes are between the bus electrodes and the user, which requires the user to look through the transparent electrodes to see the bus electrodes. The transparent electrode, therefore, obstructs the user's view of the darkened bus electrode, so that the color of the bus electrode is not clearly seen, which negatively impacts the capability of the colored bus electrode to control bright room contrast.
Additionally, external light (natural light or artificial light) may enter the PDP's front substrate and reflect off of the transparent electrode. In this instance, the reflected light may also obstruct the viewer from clearly seeing the color of the bus electrode, thereby limiting the bus electrode's capability to control bright room contrast.